An Innovative Dual-Strengthening Pretreatment to Improve Li and Co Leaching in Spent Lithium-Ion Batteries: Pyrolysis Combined with Mechanical Grinding

The presence of PVDF prevents the contact of leaching solution and LiCoO2, which is the decisive factor leading to the low leaching efficiency of electrode materials. Therefore, a dual-strengthening pretreatment method is proposed to remove PVDF more efficiently and enhance the leaching of the LiCoO2. To determine the enhanced effect of the PVDF removal and the leaching of LiCoO2 treated by dual-strengthening pretreatment, the leaching behavior of the untreated, ground, pyrolyzed and dual-strengthening pretreated LiCoO2 were compared. XPS and SEM-EDS were used to evidence the removal of the PVDF, while the XRD was used to analyze the composition of the leaching slag to evidence the leaching behavior. The XPS results show that dual-strengthening pretreatment on PVDF removal is better than that of the single treatment. SEM confirms that the electrode material can achieve the double effect of pyrolysis residue removal and particle size reduction after dual-strengthening. The leaching enhancement of dual-strengthening is more significant than the single pretreatment, and the improvement of single pyrolysis is greater than that of grinding by detecting the leaching rate of Li and Co using ICP-MS. The leaching rate of Li and Co in the dual-strengthening LiCoO2 is 96.25 % and 95.21 %, it is 95.16 % and 94.50 % in the pyrolyzed LiCoO2, while it is 73.96 % and 66.78 % in the ground LiCoO2. The mechanism of the dual-strengthening treatment lies in the full removal of PVDF to expand the dispersion of LiCoO2 particles. The present study provides an innovative strengthening approach to LiCoO2 leaching.